MySQL Shell API 8.0.29
Unified development interface for MySQL Products
Methods | List of all members
CollectionFind Class Reference

Handler for document selection on a Collection. More...

Methods

CollectionFind find (str searchCondition)
 Sets the search condition to identify the Documents to be retrieved from the owner Collection. More...
 
CollectionFind fields (str fieldDefinition[, str fieldDefinition,...])
 Sets the fields to be retrieved from each document matching the criteria on this find operation. More...
 
CollectionFind group_by (list fields)
 Sets a grouping criteria for the resultset. More...
 
CollectionFind having (str condition)
 Sets a condition for records to be considered in aggregate function operations. More...
 
CollectionFind sort (list sortCriteria)
 Sets the sorting criteria to be used on the DocResult. More...
 
CollectionFind limit (int numberOfDocs)
 Sets the maximum number of documents to be returned by the operation. More...
 
CollectionFind skip (int numberOfDocs)
 Sets number of documents to skip on the resultset when a limit has been defined. More...
 
CollectionFind offset (int numberOfDocs)
 Sets number of documents to skip on the resultset when a limit has been defined. More...
 
CollectionFind lock_shared (str lockContention)
 Instructs the server to acquire shared row locks in documents matched by this find operation. More...
 
CollectionFind lock_exclusive (str lockContention)
 Instructs the server to acquire an exclusive lock on documents matched by this find operation. More...
 
CollectionFind bind (str name, Value value)
 Binds a value to a specific placeholder used on this CollectionFind object. More...
 
DocResult execute ()
 Executes the find operation with all the configured options. More...
 

Detailed Description

Handler for document selection on a Collection.

This object provides the necessary functions to allow selecting document data from a collection.

This object should only be created by calling the find function on the collection object from which the documents will be retrieved.

See also
Collection

Member Function Documentation

◆ find()

CollectionFind find ( str  searchCondition)

Sets the search condition to identify the Documents to be retrieved from the owner Collection.

Parameters
searchConditionOptional String expression defining the condition to be used on the selection.
Returns
This CollectionFind object.

Sets the search condition to identify the Documents to be retrieved from the owner Collection. If the search condition is not specified the find operation will be executed over all the documents in the collection.

The search condition supports parameter binding.

Method Chaining

After this function invocation, the following functions can be invoked:

See also
Usage examples at execute().

◆ fields()

CollectionFind fields ( str  fieldDefinition[, str fieldDefinition,...])

Sets the fields to be retrieved from each document matching the criteria on this find operation.

Parameters
fieldDefinitionDefinition of the fields to be retrieved.
Returns
This CollectionFind object.

This function sets the fields to be retrieved from each document matching the criteria on this find operation.

A field is defined as a string value containing an expression defining the field to be retrieved.

The fields to be retrieved can be set using any of the next methods:

  • Passing each field definition as an individual string parameter.
  • Passing a list of strings containing the field definitions.
  • Passing a JSON expression representing a document projection to be generated.

Method Chaining

This function can be invoked only once after:

See also
Usage examples at execute().

◆ group_by()

CollectionFind group_by ( list  fields)

Sets a grouping criteria for the resultset.

Returns
This CollectionFind object.

Sets a grouping criteria for the resultset.

Method Chaining

This function can be invoked only once after:

See also
Usage examples at execute().

◆ having()

CollectionFind having ( str  condition)

Sets a condition for records to be considered in aggregate function operations.

Parameters
conditionA condition on the aggregate functions used on the grouping criteria.
Returns
This CollectionFind object.

Sets a condition for records to be considered in aggregate function operations.

Method Chaining

This function can be invoked only once after:

See also
Usage examples at execute().

◆ sort()

CollectionFind sort ( list  sortCriteria)

Sets the sorting criteria to be used on the DocResult.

Returns
This CollectionFind object.

If used, the CollectionFind operation will return the records sorted with the defined criteria.

Every defined sort criterion follows the format:

name [ ASC | DESC ]

ASC is used by default if the sort order is not specified.

Method Chaining

This function can be invoked only once after:

See also
Usage examples at execute().

◆ limit()

CollectionFind limit ( int  numberOfDocs)

Sets the maximum number of documents to be returned by the operation.

Parameters
numberOfDocsThe maximum number of documents to be retrieved.
Returns
This CollectionFind object.

If used, the operation will return at most numberOfDocs documents.

Method Chaining

This function can be invoked only once after:

After this function invocation, the following functions can be invoked:

See also
Usage examples at execute().

◆ skip()

CollectionFind skip ( int  numberOfDocs)

Sets number of documents to skip on the resultset when a limit has been defined.

Parameters
numberOfDocsThe number of documents to skip before start including them on the DocResult.
Returns
This CollectionFind object.

If used, the first numberOfDocs records will not be included on the result.

Attention
This function will be removed in a future release, use the offset() function instead.

Method Chaining

This function can be invoked only once after:

See also
Usage examples at execute().

◆ offset()

CollectionFind offset ( int  quantity)

Sets number of documents to skip on the resultset when a limit has been defined.

Parameters
quantityThe number of documents to skip before start including them on the DocResult.
Returns
This CollectionFind object.

If used, the first quantity records will not be included on the result.

Method Chaining

This function can be invoked only once after:

See also
Usage examples at execute().

◆ lock_shared()

CollectionFind lock_shared ( str  lockContention)

Instructs the server to acquire shared row locks in documents matched by this find operation.

Parameters
lockContentionoptional parameter to indicate how to handle documents that are already locked.
Returns
This CollectionFind object.

When this function is called, the selected documents will be locked for write operations, they may be retrieved on a different session, but no updates will be allowed.

The acquired locks will be released when the current transaction is committed or rolled back.

The lockContention parameter defines the behavior of the operation if another session contains an exclusive lock to matching documents.

The lockContention can be specified using the following constants:

  • mysqlx.LockContention.DEFAULT
  • mysqlx.LockContention.NOWAIT
  • mysqlx.LockContention.SKIP_LOCKED

The lockContention can also be specified using the following string literals (no case sensitive):

  • 'DEFAULT'
  • 'NOWAIT'
  • 'SKIP_LOCKED'

If no lockContention or the default is specified, the operation will block if another session already holds an exclusive lock on matching documents until the lock is released.

If lockContention is set to NOWAIT and another session already holds an exclusive lock on matching documents, the operation will not block and an error will be generated.

If lockContention is set to SKIP_LOCKED and another session already holds an exclusive lock on matching documents, the operation will not block and will return only those documents not having an exclusive lock.

This operation only makes sense within a transaction.

Method Chaining

This function can be invoked at any time before bind() or execute() are called.

After this function invocation, the following functions can be invoked:

If lock_exclusive() is called, it will override the lock type to be used on the selected documents.

See also
Usage examples at execute().

◆ lock_exclusive()

CollectionFind lock_exclusive ( str  lockContention)

Instructs the server to acquire an exclusive lock on documents matched by this find operation.

Parameters
lockContentionoptional parameter to indicate how to handle documents that are already locked.
Returns
This CollectionFind object.

When this function is called, the selected documents will be locked for read operations, they will not be retrievable by other session.

The acquired locks will be released when the current transaction is committed or rolled back.

The lockContention parameter defines the behavior of the operation if another session contains a lock to matching documents.

The lockContention can be specified using the following constants:

  • mysqlx.LockContention.DEFAULT
  • mysqlx.LockContention.NOWAIT
  • mysqlx.LockContention.SKIP_LOCKED

The lockContention can also be specified using the following string literals (no case sensitive):

  • 'DEFAULT'
  • 'NOWAIT'
  • 'SKIP_LOCKED'

If no lockContention or the default is specified, the operation will block if another session already holds a lock on matching documents.

If lockContention is set to NOWAIT and another session already holds a lock on matching documents, the operation will not block and an error will be generated.

If lockContention is set to SKIP_LOCKED and another session already holds a lock on matching documents, the operation will not block and will return only those documents not having a lock.

This operation only makes sense within a transaction.

Method Chaining

This function can be invoked at any time before bind() or execute() are called.

After this function invocation, the following functions can be invoked:

If lock_shared() is called, it will override the lock type to be used on the selected documents.

See also
Usage examples at execute().

◆ bind()

CollectionFind bind ( str  name,
Value  value 
)

Binds a value to a specific placeholder used on this CollectionFind object.

Parameters
nameThe name of the placeholder to which the value will be bound.
valueThe value to be bound on the placeholder.
Returns
This CollectionFind object.

Binds the given value to the placeholder with the specified name.

An error will be raised if the placeholder indicated by name does not exist.

This function must be called once for each used placeholder or an error will be raised when the execute() method is called.

Method Chaining

This function can be invoked multiple times right before calling execute().

After this function invocation, the following functions can be invoked:

See also
Usage examples at execute().

◆ execute()

DocResult execute ( )

Executes the find operation with all the configured options.

Returns
A DocResult object that can be used to traverse the documents returned by this operation.

Method Chaining

This function can be invoked after any other function on this class.

Examples

Retrieving All Documents

records = collection.find().execute().fetch_all()
print("All:", len(records), "\n")

Filtering

records = collection.find('gender = "male"').execute().fetch_all()
print("Males:", len(records), "\n")
records = collection.find('gender = "female"').execute().fetch_all()
print("Females:", len(records), "\n")

Field Selection

Using a field selection list

result = collection.find('name = "jack"').fields(['ucase(name) as FirstName', 'age as Age']).execute()
record = result.fetch_one()
print("First Name: %s\n" % record.FirstName)
print("Age: %s\n" % record.Age)

Using separate field selection parameters

result = collection.find('name = "jack"').fields('ucase(name) as FirstName', 'age as Age').execute()
record = result.fetch_one()
print("First Name: %s\n" % record.FirstName)
print("Age: %s\n" % record.Age)

Using a projection expression

result = collection.find('name = "jack"').fields(mysqlx.expr('{"FirstName":ucase(name), "InThreeYears":age + 3}')).execute()
record = result.fetch_one()
print("First Name: %s\n" % record.FirstName)
print("In Three Years: %s\n" % record.InThreeYears)

Sorting

records = collection.find().sort(['name']).execute().fetch_all()
for index in range(7):
print('Find Asc', index, ':', records[index].name, '\n')
records = collection.find().sort(['name desc']).execute().fetch_all()
for index in range(7):
print('Find Desc', index, ':', records[index].name, '\n')

Using Limit and Offset

records = collection.find().limit(4).execute().fetch_all()
print('Limit-Offset 0 :', len(records), '\n')
for index in range(8):
records = collection.find().limit(4).offset(index + 1).execute().fetch_all()
print('Limit-Offset', index + 1, ':', len(records), '\n')

Parameter Binding

records = collection.find('age = :years and gender = :heorshe').bind('years', 13).bind('heorshe', 'female').execute().fetch_all()
print('Find Binding Length:', len(records), '\n')
print('Find Binding Name:', records[0].name, '\n')